Alfalfa pellets is one of my favorite soil amendments. Not only is it a good source of NPK but it also contains a lot of different minerals and the plant hormone triacontanol, which can boost plant growth. I'll typically add alfalfa to the soil in the fall and then again in early spring prior to tilling.
Alfalfa also makes a good compost tea. It is a great way to apply triacontanol to the plant while giving it a boost of beneficial microbes. I brewed an aerated compost tea for 36 hours which contained about 1 cup of alfalfa pellets, 1 teaspoon of silica and 1/8 teaspoon of cane molasses. After the brew, I poured the tea over the leaves of the pumpkin plant and poured some on the ground as well. That gives the pumpkins a little bit of everything that it needs to grow big.